This invention relates to printing generally, and is more specifically directed to a method of printing heat activated ink by means of an ink jet printer onto paper or other printable substrate as a medium, and subsequently heat activating the ink, thereby transferring the design formed by the ink from the medium to a substrate on which the design is to permanently appear.
Words and designs are frequently printed onto clothing and other textile materials, and other objects. Common means of applying such designs to objects include the use of silk screens, and mechanically bonded thermal transfers.
The use of computer technology allows substantially instantaneous printing of images. For example, video cameras or scanning may be used to capture an image to a computer. The image may then be printed by any suitable printing means, including mechanical thermal printers, ink jet printers and laser printers. These printers will print in multiple colors.
Color ink jet printers are in common use. Color ink jet printers use combinations of cyan, yellow and magenta inks or dyes to produce multi-color images.
The primary types of ink jet printers currently in use fall into three categories: phase change, free flow, and bubble jet. The inks or dyes used in phase change ink jet printing are contained in a solid compound which changes state by the application of heat to liquify the solid, whereupon the ink composition is printed. Free flow and bubble jet printers use liquid inks, although the actual printing process of free flow ink jet printers differs from bubble jet printers.
Heat activated transfer ink solids change to a gas at about 400xc2x0 F., and have a high affinity for polyester at the activation temperature and a limited affinity for most other materials. Once the gassification bonding takes place, the ink is permanently printed and highly resistant to change or fading caused by laundry products.
Hale, U.S. Pat. Nos. 5,246,518, 5,248,363 and 5,302,223 disclose the use of thermal printers to produce an image on a medium or transfer sheet wherein the image is comprised of sublimation or other heat activated inks. The method described in Hale does not activate the ink during the printing of the medium or transfer sheet.
The process of printing heat sensitive ink solids such as sublimation inks by means of a phase change ink jet printer is similar to the process described in Hale, U.S. Pat. Nos. 5,246,518, 5,248,363 and 5,302,223. The use of heat by all ink jet printers presents the problem recognized in the Hale patents of printing heat activated inks in a non activated form by means of such printers, since the ink is exposed to high temperatures by the printer. Bubble jet printers, for example, heat the ink during the printing process to around the boiling point of the ink solvent, which is typically water. Free flow ink jet printers use heat to form pressure which transports the ink during the printing process.
The use of liquid inks, as required by free flow and bubble jet printers, presents a new set of problems when trying to print ink solids. The orifices or nozzles of free flow and bubble jet printers are not designed for the dispensing of solids contained within a liquid material. The orifices of these printers are typically 5-10 microns in diameter, and clogging of the orifice will occur when ink solids of large particle size or in high volume are transferred through the orifice.
Further, when the ink solids are placed into the liquid, the ink solids tend to separate from the liquid over time and fall to the bottom of the ink container. The ink composition is typically sealed in a container at a manufacturing facility, for subsequent mounting of the container within the ink jet printer, meaning that a substantial storage time for the ink composition exists prior to use. Separation of the liquid and solids within the ink formulation presents problems with regard to the mechanical operation of the printer and the print quality achieved from use of the ink formulation. Materials which inhibit separation must also inhibit agglomeration of the solid dye particles, while allowing, and not preventing due to insulation or otherwise, activation of the ink or dye during the final printing at elevated temperatures.
The present invention is a method of printing heat activated ink solids in a non activated form onto a medium in a desired image by means of an ink jet printer, for subsequent transfer of the image from the medium by heat activation of the ink solids. The invention includes ink or dye compositions comprising heat activated ink or dye solids for use with the method. The ink compositions presented include solid compositions at ambient temperature for use with phase change ink jet printers, and emulsions or colloids for use with free flow and bubble jet printers.
The ink solids are transferred in the desired design by means of a printer onto a substrate, which acts as a medium. The substrate may be paper, or it may be other material which will facilitate and withstand the transfer temperature, and which facilitates bonding of the ink layer to the substrate.
The ink jet printer incorporates a thermal process, but the ink solids of the invention do not activate at the operational temperatures of the printer. Heat activation of the ink solids does not take place at the time of printing of the image by the printer, but rather, takes place at the time of the transfer of the image from the medium to the substrate on which the image is permanently applied. The non activated ink solids produce a printed image on the medium which is recognizable, but the colors are dull and are not acceptable for most applications.
Sufficient temperature is then applied to the image to transfer the image from the medium to the substrate on which the image is to permanently appear . The heat activates, or sublimates, the ink solids during this transfer from the medium to the substrate. The image is then permanently bonded to the substrate. The permanent image is sharp, with vivid colors forming the image.
When the ink formulation prepared according to the invention is a liquid, finely divided dye solids are present in a liquid carrier, in a colloidal or emulsion form. An emulsifying enforcing agent, which has characteristics of a surfactant, surrounds and shields the dye particles to prevent undesired activation at low heat and to prevent agglomeration of the dye particles. However, the emulsifying enforcing agent allows activation of the dye at higher temperatures.